KR101073325B1 - Brushless Motor - Google Patents

Abstract

An object of the present invention is to provide a brushless motor that realizes a high-precision detection of magnetic pole positions even when using an approximate sine wave sensorless drive. A brushless motor according to the present invention includes a rotating body rotating with a central axis as a rotating shaft, a rotor magnet coaxially disposed with the rotating body, a stator facing the rotor magnet, and a coil wound around the stator. The sensorless driving circuit drives the brushless motor based on a signal including a harmonic component tripled with respect to the fundamental wave of an organic voltage, and the rotor magnet rotates with respect to the stator so that the coil is rotated. It is characterized in that the amplitude ratio of triplex harmonics to the fundamental wave of the induced voltage generated at is 1% or more. According to the present invention, it is possible to provide a brushless motor that realizes high-precision detection of magnetic pole positions while using an approximate sine wave sensorless drive.

Description

Brushless Motor {BRUSHLESS MOTOR}

The present invention relates to a motor driven by a sensorless drive circuit.

Background Art Conventionally, brushless motors have been driven by pulse width modulation (PWM) using inverter devices for a wide range of variable speed control and current consumption reduction. For example, a position sensor such as a hall element for detecting the magnetic pole position of the rotor magnet is disposed at an electric angle of 120 degrees inside a brushless motor having a three-phase coil. The brushless motor drives the approximate sine wave by driving each switching element in the inverter device based on a signal corresponding to the magnetic pole position obtained by these position sensors.

In addition, for the purpose of reducing the cost and size of the brushless motor, various sensorless driving techniques have not been developed that use a position sensor. As a means of realizing this sensorless drive, there exists a method of detecting the zero cross point of the induced voltage which generate | occur | produces in a non-conduction period using the 120 degree electricity supply system or the wide angle electricity supply method of less than 180 degree. Therefore, in these energization methods, a non-energization period is required for each phase in order to detect a magnetic pole position. Therefore, the presence of the non-energization period caused it, and the vibration and the noise accompanying this vibration generate | occur | produced in the timing of electricity supply switching.

Therefore, recently, an approximate sine wave sensorless drive that realizes low vibration and low noise that does not require a non-energization period has been developed. See Patent Document 1).

(Patent Document 1) Japanese Patent Laid-Open No. 2006-230120

Here, in the approximate sine wave sensorless driving, instead of the non-energization period, 3N times harmonic components (N is a positive integer) superimposed on the induced voltage are used instead of the non-energization period. Therefore, when the induced voltage is small due to the low speed rotation and when the amplitude ratio of triple harmonics is extremely small, there is a problem that the magnetic pole position cannot be detected with high accuracy.

Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a brushless motor that realizes high-precision detection of magnetic pole positions even when using an approximate sine wave sensorless drive.

According to claim 1 of the present invention, a brushless motor driven by a sensorless drive circuit, comprising: a rotating body rotating with a central axis as a rotating shaft; a rotor magnet coaxially arranged with the rotating body; And a stator facing the rotor magnet, and a coil wound around the stator, wherein the sensorless driving circuit drives and controls the brushless motor based on a signal including triplex harmonic components with respect to the fundamental wave of the induced voltage. And the rotor magnet is rotated with respect to the stator so that the amplitude ratio of triplex harmonics to the fundamental wave of the induced voltage generated in the coil is set to be 1% or more. .

According to claim 2 of the present invention, a brushless motor, comprising: a rotor having a rotor magnet disposed coaxially with a central axis and rotating around the central axis, a stator facing the rotor magnet, and a coil of the stator. And a stationary body having a sensorless driving circuit for controlling rotation of the rotating body by controlling energization of the rotating body, wherein the sensorless driving circuit is generated in the coil by rotating the rotor magnet with respect to the stator. A position detector for detecting the rotational position of the rotating body from the induced voltage, a control unit for controlling the energization timing according to the positional information of the rotating body obtained from the position detecting unit, and a control signal from the control unit to the coil. And a motor drive unit for switching energization, wherein the position detection unit The position of the rotating body is detected using a signal including triplex harmonic components with respect to the fundamental wave of pressure, and the induced voltage is set such that the amplitude ratio of the triplex harmonic to the fundamental wave is 1% or more. A brushless motor is provided.

According to Claims 1 and 2 of the present invention, when the amplitude ratio of triplex harmonics is 1% or more with respect to the fundamental wave of the induced voltage, the brushless motor can be normally rotated by the sensorless driving circuit. In addition, the brushless motor of the present invention may be provided with a sensorless drive circuit outside the brushless motor.

According to the third aspect of the present invention, the magnetic flux density of the side surface of the rotor magnet is distributed in a waveform having an approximate sine wave shape with respect to the rotation angle, and the concave portion is present at the center of the magnetic pole in the waveform.

According to claim 3 of the present invention, by providing a concave portion at the pole center of the magnetic flux density waveform on the side of the rotor magnet, it can contain three times the harmonics with respect to the fundamental wave of the organic voltage. Therefore, the brushless motor can be rotated more normally by the sensorless driving circuit.

According to claim 4 of the present invention, the ratio of the change amount which is the difference between the maximum value and the minimum value of the coil inductance to the maximum value of the coil inductance is about 10% or more.

According to claim 4 of the present invention, the amplitude of the induced voltage waveform can be increased when the amount of change in the coil inductance with respect to the maximum value of the coil inductance is about 10% or more. Therefore, even when the brushless motor is rotated at low speed (for example, 40 revolutions per minute), the brushless motor can be rotated normally.

According to claim 5 of the present invention, the stator extends along a radial direction about a central axis, and has a plurality of teeth portions spaced apart in the circumferential direction, and the teeth portion has a widening portion and the widening portion facing the rotor magnet. A base portion extending radially inwardly from the portion, wherein the widening portion is provided on an opposite surface having a width in the circumferential direction that is larger than the width in the circumferential direction of the base portion, and provided on an opposite side of the opposite surface and the radial direction; The value of D1 / R1 which has an inner surface continuous with the side surface of a base part, and which is the ratio of the position which is closest to the said rotor magnet of the said opposing surface, and the distance R1 which connected the said central axis, and the distance D1 which connected the said inner surface and the said central axis is about It is characterized by being 0.92 or less.

According to claim 5 of the present invention, when the value of D1 / R1 is about 0.92 or less, the change in the coil inductance can be changed in accordance with the change in the magnetic flux density of the magnetic pole of the rotor magnet. Therefore, the brushless motor can be rotated more normally by the sensorless driving circuit.

According to the sixth aspect of the present invention, the size of the width in the circumferential direction of the base portion is changed along the radial direction, and the maximum value Wmax of the width in the circumferential direction of the base portion and the width in the circumferential direction of the base portion. The value of Wmin / Wmax, which is the ratio of the minimum value Wmin, is characterized by being about 0.7 or more.

According to claim 6 of the present invention, when the value of Wmin / Wmax is about 0.7 or more, the change in the coil inductance can be changed in accordance with the change in the magnetic flux density of the magnetic pole of the rotor magnet. Therefore, the brushless motor can be rotated more normally by the sensorless driving circuit.

According to the seventh aspect of the present invention, the sensorless driving circuit is configured on a circuit board constituting the fixed body.

According to claim 7 of the present invention, since the sensorless driving circuit is configured on the circuit board of the fixed body of the brushless motor, it is not necessary to include a circuit board for the sensorless driving circuit in addition to the brushless motor. A device equipped with a lease motor can be miniaturized.

According to the eighth aspect of the present invention, the rotating body includes a mounting portion that mounts a disk-shaped disk having an opening hole in the center thereof, and a chucking device that allows the disk to be detachable.

According to claim 8 of the present invention, even if the disk is directly rotated by the brushless motor, it is possible to provide a highly reliable brushless motor that rotates normally.

According to the ninth aspect of the present invention, there is provided a disk drive device that mounts the brushless motor according to claim 8 to drive a disk, comprising: an optical pickup mechanism for performing light emission and light reception on the disk, and the optical pickup mechanism in a radial direction; There is provided a disk drive device comprising a moving mechanism that enables movement to a side surface.

According to claim 9 of the present invention, it is possible to provide a highly reliable disk drive apparatus which prevents recording and reproduction errors while achieving low vibration and low noise.

According to the present invention, it is possible to provide a brushless motor that realizes high-precision detection of magnetic pole positions while using an approximate sine wave sensorless drive.

(Whole structure of brushless motor)

One embodiment of the brushless motor of the present invention will be described with reference to FIGS. 1 and 2. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section which cut | disconnected one Embodiment of the brushless motor of this invention in the axial direction. 2 is a plan view of the brushless motor of FIG. 1 seen from above.

Referring to FIG. 1, the brushless motor 10 has a surface facing radially with the rotor 20 and the rotor magnet 23 having a rotor magnet 23 rotating around a predetermined central axis J1. It consists of the fixed part 30 which has the stator 33 which has. The brushless motor 10 is a three-phase drive spindle motor which rotates an optical disk such as a CD or a DVD about the central axis J1.

First, the rotating unit 20 will be described.

The rotating part 20 includes a shaft 21 coaxially disposed with the central axis J1, a rotor holder 22 fixed to the shaft 21, a rotor magnet 23 fixed to the rotor holder 22, A chucking device 24 disposed above the rotor holder 22 is provided.

The rotor holder 22 includes a substantially cylindrical shaft fixing portion 221 fixed to the outer circumferential surface of the shaft 21, a cover portion 222 which is a plane extending radially from an axially lower side of the shaft fixing portion 221, and , A cylindrical portion 223 extending downward from the outer edge of the lid portion 222 in the axial direction. In addition, a substantially cylindrical rotor magnet 23 is fixed to the inner circumferential surface of the cylindrical portion 223. Here, the number of poles of the rotor magnet 23 of the brushless motor 10 of the present embodiment is 16. The rotor magnet 23 is a neodium magnet (Nd-Fe-B).

On the outer side in the radial direction of the cover part 222 of the rotor holder 22, the mounting part 224 which is a plane substantially parallel to the cover part 222 bent upward in the axial direction is formed. On the radially outer side of the mounting portion 224, a mounting surface 2241 made of an annular rubber is provided.

The chucking device 24 is fixed to the outer peripheral surface of the shaft fixing part 221 of the rotor holder 22. The chucking device 24 includes a center case 241 in contact with a central opening of a disc (not shown), and three coil springs 242 (three in this embodiment) accommodated in the center case 241. See FIG. ) And the chuck claws 243 (three in this embodiment, see FIG. 2) to which a force is applied radially outward by the coil spring 242. This chuck claw 243 holds the disk by contacting the upper edge of the center opening of the disk. In addition, the center case 241 is provided with a claw 2411 (three in this embodiment, see FIG. 2) integrally. Then, the claws 2411 come in contact with the central opening of the disc, so that the center of the central opening and the central axis J1 are adjusted to coincide.

Next, the fixing part 30 is demonstrated.

The fixing part 30 has a substantially cylindrical sleeve 31 having an inner circumferential surface rotatably supporting the shaft 21 in a radial direction, a housing 32 having an inner circumferential surface holding the outer circumferential surface of the sleeve 31, and a housing ( The stator 33 fixed to the 32, the mounting plate 34 fixed to the housing 32 and disposed axially downward from the stator 33, and the circuit board 35 fixed to the upper surface of the mounting plate 34. ), A disk-shaped plate 36 fixed to the housing 32 and covering the axially lower side of the inner circumferential surface of the housing 32, and a thrust plate 37 disposed on the upper surface of the plate 36. Here, the bearing part is constituted by the sleeve 31 and the thrust plate 37.

The housing 32 is composed of a base portion 321 for fixing the stator 33 and a substantially cylindrical cylindrical portion 322 extending upward from the base portion 321 in the axial direction. The inner circumferential surface of the housing 32 is composed of an inner circumferential surface of the base portion 321 and an inner circumferential surface of the cylindrical portion 322.

The stator 33 is fixed to the first outer circumferential end 3211 formed above the base portion 321. The attachment plate 34 is fixed to the second outer circumferential end 3212 formed below the base portion 321. In addition, the plate 36 is fixed to the inner circumferential end 3213 formed below the base portion 321.

On the axially upper side of the cylindrical portion 322 of the housing 32, a hooking portion 3221 protruding toward the radially outer side is formed integrally with the cylindrical portion 322. The outer circumferential surface of the hanging portion 3221 has an inclined surface that is inclined outward in the radial direction toward the lower side in the axial direction. Moreover, the fall prevention member 25 is fixed to the lower surface of the cover part 222 of the rotor holder 22. This hooking part 3221 and the fall prevention member 25 play a role which restricts the movement of the rotating part 20 to an axial upper side.

The stator 33 is composed of a stator core 331 in which a plurality of thin plate-shaped magnetic plates are laminated in the axial direction, and a plurality of coils 332 formed by winding a conductive wire around the stator core 331. The outer circumferential surface of the stator core 331 is disposed to face the inner circumferential surface of the rotor magnet 23 in the radial direction. These coils 332 are collectively referred to as windings. The coil consists of three phases of U phase, V phase and W phase, and is connected by Y connection. Here, in the plurality of coils 332, the group of coils 332 constituting the U phase is Lu, the group of coils 332 constituting the V phase is Lv, and the group of coils 332 constituting the W phase is Lw. It is prescribed | regulated (refer FIG. 3).

By passing a current through the coil 332 of the stator 33, the stator 33 generates a magnetic field. And the rotor magnet 23 and the stator 33 form a rotating magnetic field, the rotational torque centering on the center axis J1 generate | occur | produces, and the rotating part 20 rotates.

Moreover, the information of the pattern forming part 141 formed in the label surface which is the back surface of a disk (not shown) is optically read from the rotating body 20 in the mounting plate 34 on the outer side in a radial direction. The position detection mechanism 38 (refer FIG. 2) is attached. And when drawing a character or a figure on the label surface of a disk, the rotation body 20 is controlled to rotate at low speed (for example, 40 revolutions per minute) based on the information which the position detection mechanism 38 produces. do. In addition, the position detection mechanism 38 is a photosensor here, for example.

(Structure of Approximate Sine Wave Sensorless Driving Circuit)

Next, the overall structure of the approximate sine wave sensorless driving circuit will be described with reference to FIG. 3. 3 is a circuit diagram showing the overall structure of the approximate sine wave sensorless driving circuit for driving the brushless motor of the present invention. Here, the approximate sine wave sensorless driving circuit corresponds to the sensorless circuit of the claims.

The approximate sine wave sensorless drive circuit 4 is configured on the circuit board 35. Therefore, since the brushless motor 10 and the approximate sine wave sensorless drive circuit 4 are not separated, the brushless motor 10 can be used for the approximate sine wave sensorless drive circuit 4 in addition to the brushless motor 10. No circuit board is required. Therefore, the apparatus (for example, disk drive apparatus) which mounts the brushless motor 10 can be miniaturized.

Referring to FIG. 3, the approximate sine wave sensorless drive circuit 4 includes a motor drive unit 41, a magnetic pole position detection unit 42, and a control unit 43.

The motor driver 41 is disposed between the power source 44 and the ground GND. And the motor drive part 41 is comprised from six transistors 411-416 (field effect transistor in this embodiment) bridged. Diodes 411a to 416a are connected in reverse parallel to the transistors 411 to 416, respectively. The transistors 411, 412, 413 are connected in series with the transistors 414, 415, 416, respectively. Here, the transistors 411, 412, 413 constitute the upper arm of the motor driver 41, and the transistors 414, 415, 416 constitute the lower arm of the motor driver 41.

The magnetic pole position detector 42 includes a sample hold circuit 421, a low pass filter 422, a comparator 423, and a DC power supply having a reference voltage Vr. The sample hold circuit 421 includes a switch 4211 and a condenser 4212.

The control unit 43 includes a command voltage generator 431, a drive signal generator 432, a command unit 433, an error amplifier 434, a triangle wave generator 435, and a current detector 436. ) And a sample hold signal generator 437.

The current detector 436 detects the magnitude of the current flowing through the motor driver 41. The current detection signal CS, which is the detection result of the current detection unit 436, is output to the error amplifier 434. The command part 433 generates the torque command signal EC which designates the torque added to the brushless motor 10. The error amplifier 434 amplifies the error between the target current value and the current detection signal CS obtained from the torque command signal EC. The error amplifier 434 then outputs the error amplified signal Va indicating the error result to the command voltage generator 431 and the sample hold signal generator 437, respectively.

The sample hold signal generator 437 receives the error amplified signal Va and the triangular wave signal Vtri generated from the triangular wave generator 435, and the transistors 414 to 416, which are lower arms of the motor driver 41, are all turned on ( The sample hold signal SH1, which is a timing pulse indicating the timing at which the signal is turned ON), is output to the stimulus detector 42.

The stimulus detector 42 samples and holds the neutral point voltage Vc of the brushless motor 10 according to the signal level of the sample hold signal SH1. Thereby, the magnetic pole detection part 42 detects the magnetic pole position of the rotor magnet 23, ie, the phase of the induced voltage which arises in each phase. The stimulus detector 42 then outputs the position detection signal FG indicating the detection result to the command voltage generator 431.

The switch 4211 of the magnetic pole detection unit 42 performs the opening and closing operation according to the signal level (H level, L level) of the sample hold signal SH1. When the signal level of the sample hold signal SH1 is H level, the switch 4211 closes and a short circuit state occurs. As a result, the neutral point voltage Vc of the brushless motor 10 is detected by the capacitor 4212 (sampling operation).

Next, when the sample hold signal SH1 is at L level, the switch 4211 is opened to enter the open state. As a result, the capacitor 4212 maintains the sampled voltage (hold operation). As described above, the sample hold circuit 421 outputs the sample hold output signal VcSH1 by performing a sample hold operation of the neutral point voltage Vc of the brushless motor 10 in accordance with the signal level of the sample hold signal SH1. This sample hold output signal VcSH1 is input to the low pass filter 422. The low pass filter 422 smoothes the sample hold output signal VcSH1 by removing the step included in the sample hold output signal VcSH1. In addition, the low pass filter 422 outputs a signal VcSH2 from which the step is removed, to the comparator 423. The signal VcSH2 is input to one input terminal of the comparator 423, and the reference voltage Vr of the power supply is input to the other input terminal. And the comparator 423 generates the position detection signal FG which is a pulse signal.

The command voltage generator 431 generates the sinusoidal three-phase command voltages sinU, sinV, and sinW based on the position detection signal FG and the error amplification signal Va from the stimulus detector 42, respectively. These three-phase command voltages sinU, sinV, and sinW are 180-degree energized waveforms whose phase differences are 120 degrees, respectively. The command voltage generator 431 then outputs the three-phase command voltage to the drive signal generator 432. The drive signal generator 432 outputs a drive signal to the transistors 411 to 416 of the motor driver 41 using the three-phase command voltage.

In addition, since the transistors 414 to 416 of each phase are all turned on, the sample hold output signal VcSH1 of the stimulus detector 42 is a voltage that overlaps each of the 3N times harmonic components (N is a positive integer) included in the induced voltage. do. In addition, since the sample hold output signal VcSH1 is extremely small compared to the triplex harmonic component, such as the sixth harmonic component, the nineth harmonic component, and the like, the voltage is caused by the triplex harmonic component. Therefore, the amplitude Na of the sample hold output signal VcSH1 is represented by the product of C, that is, the ratio of the amplitude of triplex harmonic components to the fundamental wave amplitude A of the induced voltage, that is, Na = A × C. When the sample hold output signal VcSH1 has a large amplitude, the magnetic pole position can be detected with high accuracy.

In addition, by using the approximate sine wave sensorless driving circuit 4 in the brushless motor of the present invention, the non sine wave sensorless driving circuit 4 does not have a non-energizing period, so that vibrations generated in the non-energizing period and It is possible to provide a low vibration and low noise brushless motor which eliminates the noise caused by the vibration.

(The details of the structure of the brushless motor)

Next, a structure for improving the amplitude ratio of triplex harmonics to the induced voltage of the brushless motor 10 of the present invention and a structure for improving the variation of the coil inductance will be described with reference to FIGS. 4 to 8. 4 is a graph showing the magnetic flux density of the rotor magnet 23 of the brushless motor 10 of the present invention as a waveform of rotation angle. 5 is a magnetic flux density of the rotor magnet of the first comparative example. 6 is a schematic plan view seen from above showing the stator 33 of the brushless motor 10, and FIG. 7 is an enlarged view in which a part of the stator core of the stator 33 is enlarged. FIG. 8 is a graph showing the coil inductance of the stator 33 of the present embodiment and the stator of the brushless motor of the second comparative example as a waveform of rotation angle. In the brushless motor of the first comparative example of Fig. 5, only the magnetization method of the rotor magnet is changed. And in the brushless motor of the 2nd comparative example in FIG. 8, only the shape of the tooth part of a stator is changed.

Referring to FIG. 4, the vertical axis of the graph in FIG. 4 represents the magnitude of the magnetic flux density (unit: Tesla), and the horizontal axis represents the rotation angle (unit: degree) about the central axis J1.

The magnetic flux density waveform 231 of the side surface (for example, the inner circumferential surface) of the rotor magnet 23 is formed as a waveform of an approximate sine wave with respect to the rotation angle (solid wave waveform in FIG. 4). That is, the rotor magnet is magnetized so that the magnetic flux density on its side has an approximate sinusoidal distribution with respect to the rotation angle. The magnetic pole center of the rotor magnet 23 is near the local maximum and the local minimum of the amplitude of the magnetic flux density waveform 231, respectively. The vicinity of the magnetic flux density waveform 231 becomes zero is the boundary of the magnetic pole. In the vicinity of the local maximum and the local minimum of the amplitude of the magnetic flux density waveform 231, recesses 2311 which are concave toward zero are provided. In addition, the waveform of the broken line in FIG. 4 shows the magnetic flux density waveform 232 of 3rd harmonic.

The magnetizer which magnetizes the rotor magnet of the present invention is provided with a recess at a position corresponding to the center of the magnetic pole of the rotor magnet of the magnetizing portion opposing the inner circumferential surface of the rotor magnet. Therefore, the magnetizing part of the magnetizing machine has an annular shape formed by the plurality of arc-like outer peripheral surfaces being spaced apart in the circumferential direction. The outer circumferential surface of the magnetized portion is disposed so as to face the inner circumferential surface of the rotor magnet via a gap in the radial direction. By providing the recessed portion in the magnetizing portion, only the recessed portion at the time of magnetization of the rotor magnet differs in the size of the gap in the radial direction between the other portion of the magnetizing portion and the inner circumferential surface of the rotor magnet, so that the magnetic flux density to be magnetized is changed. Further, for example, the rotor magnet may be magnetized by using a magnetizer having 16 concave parts but generally the same as that of the magnetizer disclosed in Japanese Patent No. 3599547. Thereby, the magnetic flux density waveform 231 of the rotor magnet 23 can be made into the shape which has the recessed part 2311.

With reference to FIG. 5, the vertical axis of the graph of FIG. 5 shows the magnitude of the magnetic flux density Tesla, and the horizontal axis shows the rotation angle (degree) about the center axis J1.

The magnetic flux density waveform 231a of the side surface (for example, the inner circumferential surface) of the rotor magnet of the brushless motor of the first comparative example is formed as a waveform of a sine wave with respect to the rotation angle (waveform of solid line in FIG. 5). That is, the rotor magnet is magnetized so that the magnetic flux density on its side has a distribution of sinusoids with respect to the rotation angle. Moreover, the recessed part 2311 like the magnetic flux density waveform of the rotor magnet 23 of the brushless motor 10 of this embodiment is not formed. Moreover, the waveform of the broken line in FIG. 5 shows the magnetic flux density waveform 232a of 3rd harmonic.

4 and 5, the amplitude of the magnetic flux density waveform 232 of the triple harmonics of the brushless motor 10 of the present embodiment is the magnetic flux density waveform of the triple harmonics of the brushless motor of the first comparative example. It can be seen that it is larger than the amplitude of 232a. As a result, the amplitude ratio of the triplex harmonic to the fundamental wave of the induced voltage of the brushless motor of the first comparative example is about 0.43%, whereas the amplitude ratio of the induced wave of the induced voltage of the brushless motor 10 of the present embodiment is three. The amplitude ratio of the harmonics is improved to about 1.36%.

Here, the brushless motor of the present invention is applied to the outer diameter of the rotor holder in the range of about 26 to about 30 (the outer diameter of the rotor holder 22 of the present embodiment is about 26). The rotation speed is used in the range of about 40 revolutions per minute to about 7000 revolutions per minute. In addition, the number of turns of the conductive wire forming the coil is about 20 to 100 times in one tooth portion of the stator (about 60 times in this embodiment). These conductive lines are wound by the same number of turns in each tooth portion. In addition, the maximum value of the magnetic flux density of the rotor magnet is about 0.2 Tesla.

Under these conditions, it was found that in order to drive the brushless motor normally, the amplitude ratio of the triplex harmonic to the fundamental wave of the induced voltage needs to be about 1% or more. That is, when the amplitude ratio of triplex harmonics to the fundamental wave of the induced voltage is lower than about 1%, the brushless motor does not reach the designated rotational speed, or the rotational speed drops once when the brushless motor is started (i.e., There is a problem that a driving abnormality such as a brushless motor does not start smoothly) occurs. However, the present invention can prevent occurrence of the above problems by setting the amplitude ratio of triplex harmonics relative to the fundamental wave of the induced voltage to about 1% or more. Therefore, a highly reliable brushless motor can be provided.

Referring to FIG. 6, the stator core 331 of the stator 33 includes a plurality of annular core bags 3311 that extend about the central axis J1 and radially outward from the core bags 3311. It is comprised from the teeth part 3312 (12 provided in this embodiment). Each coil 332 is formed by winding a conductive line in each tooth portion 3312 a plurality of times. In this embodiment, four coils of a U phase, a V phase coil, and a W phase coil are provided, respectively. The core back portion 3311 and the tooth portion 3312 are integrally formed.

Referring to FIG. 7, the tooth portion 3312 includes a base portion 3312a on which conductive lines are wound, and an expanded portion 3312b provided radially outward from the base portion 3312a. The width in the circumferential direction of the widening portion 3312b is larger than the width in the circumferential direction of the base portion 3312a.

The width in the circumferential direction of the base portion 3312a is formed to be wider in the radial direction outward. The widening portion 3312b has an inner surface constituting a plane substantially perpendicular to the extending direction in the center of the circumferential direction of the base portion 3312a and a radial direction with the inner circumferential surface of the rotor magnet 23 (see FIG. 1). It consists of opposing outer peripheral surfaces. The width in the radial direction of the widening portion 3312b is formed to be smaller toward both ends at the center in the circumferential direction of the widening portion 3312b.

Here, the outermost diameter from the central axis J1 of the tooth part 3312 is the diameter R1 and the distance from the central axis J1 to the inner surface of the wide part 3312b is D1 and the width in the circumferential direction of the base part 3312a. The maximum value of Wmax and the minimum value of the width in the circumferential direction of the base portion 3312a are defined as Wmin.

The shape of the tooth portion 3312 satisfies the range of D1 divided by R1, that is, the value of D1 / R1 of 0.85 to 0.92. The shape of the tooth portion 3312 satisfies the range obtained by dividing Wmin by Wmax, that is, a value of Wmin / Wmax of 0.7 to 0.8.

In addition, the shape of the teeth of the stator of the second comparative example is in the range of 0.93 to 1 (where D1 / R1 does not include 1) and the value of Wmin / Wmax is 0.6 to 0.7. Satisfies

With reference to FIG. 8, the vertical axis | shaft in FIG. 8 shows the magnitude | size of coil inductance (μH), and the horizontal axis shows the rotation angle (degree) of the rotor magnet 23. As shown in FIG.

The coil inductance waveform 233 (the waveform of the solid line in FIG. 8) of the brushless motor 10 of this embodiment is formed in the waveform of an approximate sine wave with respect to the rotation angle. The vicinity of the peak 2233 of the protrusion on the upper side of the coil inductance waveform 233 indicates the boundary of the magnetic pole of the rotor magnet 23. In addition, the vicinity of the apex 2332 of the protruding portion below the coil inductance waveform 233 indicates the center of the magnetic pole of the rotor magnet 23. In the coil inductance waveform 233, the waveform from the center of the magnetic pole of the rotor magnet 23 to the center of the magnetic pole adjacent in the circumferential direction, that is, the waveform between the adjacent minimum values Tb of the coil inductance waveform 233 is approximately smooth. It is shaped like a child. Here, the maximum value Ta of the coil inductance waveform 233 is defined as the maximum value of the coil inductance waveform 233 in one rotation of the rotor magnet 23 (mechanical angle 360 degrees). The minimum value Tb of the coil inductance waveform 233 is defined as the minimum value of the coil inductance waveform 233 in one rotation of the rotor magnet 23 (mechanical angle 360 degrees). Since the coil inductance waveform 233 has an inverted U shape, the value of the difference Ta-Tb between the maximum value Ta and the minimum value Tb can be increased. The value of this Ta-Tb, that is, the change (amplitude) of the coil inductance waveform is approximately proportional to the change (amplitude) of the waveform of the induced voltage. Therefore, since the change (amplitude) of the waveform of the induced voltage can be increased by increasing the change (amplitude) of the coil inductance waveform, the amplitude of the triplex harmonic can be increased.

In addition, the coil inductance waveform 233a (waveform of broken line in FIG. 8) of the brushless motor of the second comparative example is not formed as a waveform of an approximate sine wave with respect to the rotation angle. At the boundary of the magnetic pole of the rotor magnet, the recess 233a1 is provided in the coil inductance waveform 233a. Therefore, by providing the recessed part 233a1, the maximum value is not formed in the boundary part of the magnetic pole of a rotor magnet. In addition, the coil inductance waveform 233a has two maximum values in one magnetic pole of the rotor magnet. Therefore, in one magnetic pole of the rotor magnet, the coil inductance waveform 233a may be detected as having a boundary of two magnetic poles.

8, the recessed part 233a1 is provided, and the value of Tc-Td which is the difference of the maximum value Tc and the minimum value Td of the coil inductance waveform 233a becomes the brushless motor 10 of this invention. As can be seen, the coil inductance waveform 233 is significantly smaller. Here, the maximum value Tc of the coil inductance waveform 233a is the maximum value of the coil inductance waveform 233a in one rotation of the rotor magnet (360 degrees of machine angle). The minimum value Td is the minimum value of the coil inductance waveform 233a in one rotation of the rotor magnet (360 degrees of machine angle). Thereby, the amplitude of the induced voltage of the brushless motor of a 2nd comparative example will become small. As a result, a problem arises in that the brushless motor cannot be driven normally. That is, when the shape of the tooth portion is larger than about 0.92, the coil inductance waveform 233a brings the recessed portion 233a1, which causes a problem that the brushless motor cannot be driven normally. In addition, when the value of Wmin / Wmax is larger than 0.7, the tendency of formation of the recessed part 233a1 of the coil inductance waveform 233a becomes stronger. This also causes a problem that the brushless motor cannot be driven normally.

Here, in order to drive the brushless motor more normally, it was found that a value obtained by dividing the difference between the maximum value and the minimum value of the coil inductance waveform by the maximum value as a percentage, that is, the change rate of the coil inductance waveform is required to be about 10% or more. Thereby, since the amplitude of the induced voltage of a brushless motor can be enlarged, the amplitude of the triplex harmonic contained in an induced voltage can also be enlarged.

By the magnetic flux density waveform 231 and the coil inductance waveform 233 of the rotor magnet 23 of the present invention, the amplitude ratio of the harmonics three times the organic voltage is increased while increasing the amplitude of the induced voltage of the brushless motor 10. Since it is possible to improve, the amplitude of the sample hold output signal VcSH1 (see FIG. 3) can be increased. Therefore, the magnetic pole position detecting unit 42 (see FIG. 3) of the approximate sine wave sensorless driving circuit 4 can detect the magnetic pole position of the rotor magnet 23 with high accuracy. As a result, the brushless motor can be driven normally while using the approximate sine wave sensorless driving circuit with low vibration and low noise as compared to the wide-angle energizing sensorless driving circuit (that is, it is possible to prevent an abnormal driving of the brushless motor). ).

In addition, when drawing pictures or characters on the label surface that is the surface opposite to the recording surface of the optical disk, the brushless motor 10 needs to be rotated at about 40 revolutions per minute. In this case, the amplitude of the induced voltage of the brushless motor 10 becomes smaller than the amplitude of the induced voltage of normal rotation (thousands of revolutions per minute). However, by the magnetic flux density waveform 231 and the coil inductance waveform 233 of the rotor magnet 23 of the present invention, the amplitude ratio of the harmonics three times the harmonic voltage of the brushless motor 10 is increased. Since the magnetic pole position detecting unit 42 of the approximate sine wave sensorless driving circuit 4 can be improved, the magnetic pole position of the rotor magnet 23 can be detected with high accuracy.

(Overall Structure of Disk Drive Unit)

One embodiment of the disk drive device of the present invention will be described with reference to FIG. 9. It is a schematic cross section cut in the axial direction which shows one form of the Example of the disk drive apparatus of this invention.

With reference to FIG. 9, the disc drive device 50 is coaxially with the center of rotation of the disc 60 by being inserted into the aperture hole 61 of the disc-shaped disc 60 with the aperture hole 61 at the center. And a spindle motor 51 for rotating the disk 60 about the central axis J1, and an optical pickup mechanism 52 for emitting light to the disk 60 and receiving light reflected from the disk 60. And a moving mechanism 53 for moving the optical pickup mechanism 52 in the rotational radial direction of the disk 60, and a housing body 54 for housing the optical pickup mechanism 52.

The spindle motor 51 and the optical pickup mechanism 52 are held by the chassis 55. By moving the chassis 55 at least in the axial direction, the opening hole 61 of the disk 60 is attached to the chucking device of the spindle motor 51. In addition, an opening hole is formed in the chassis 55, and the optical pickup mechanism 52 is disposed inside the opening hole.

The movement mechanism 53 is provided with the motor 531 which has a gear in an output shaft, and the to-be-transmitted side gear 532 which receives the rotational torque of this motor 531.

In the housing body 54, a boundary plate 541 formed of a thin plate that separates the movement of the disk 60 and the movement mechanism 53 is formed. The housing body 54 is formed with an opening hole 542 for inserting and taking out the disk 60.

The pick-up mechanism 52 emits light, for example, a laser beam, or a light emitting portion 521 for receiving a laser beam reflected from the disk 60, and a rotation diameter of the disk 60 of the light emitting portion 521. The moving part 522 is provided perpendicular to the moving direction in the direction, and performs the movement of the light-emitting light receiving part 521. This moving part 522 has an engaging part 522a which meshes with the to-be-transmitted side gear 532. Then, the light emitting portion 521 is moved in the radial direction by engaging with the moving portion 522.

When the gear part 531a attached to the motor 531 and the gear side gear 532 mesh with each other, the gear to be transferred side 532 rotates, and the gear to be transferred side 532 moves to the moving part 522. The engaging portion 522 moves in the rotational radial direction by engaging the engaging portion 522a. And the light-emitting light-receiving part 521 moves in the rotation radial direction by the movement of this moving part 522. As shown in FIG.

By applying the brushless motor 10 of the present invention to the spindle motor 51 of the disk drive device 50, it is possible to prevent abnormal driving of the brushless motor 10 while achieving low vibration and low noise. Therefore, the optical disk can be rotated normally. Therefore, it is possible to provide a highly reliable disk drive apparatus which prevents recording and reproduction errors while achieving low vibration and low noise.

As mentioned above, although embodiment of the brushless motor and disk drive apparatus of this invention was described, this invention is not limited to the said embodiment, A various deformation | transformation is possible.

The brushless motor 10 of the present invention was a spindle motor for rotating optical disks such as CDs and DVDs, but the present invention is not limited thereto. For example, you may apply this invention to the brushless motor mounted in office equipment, a vehicle, etc.

In addition, although the approximate sine wave sensorless drive circuit 4 of the brushless motor 10 of this invention was described, the approximate sine wave sensorless drive circuit of this invention is not limited to this embodiment.

Moreover, it is realized by providing the concave part 2311 in the magnetic pole center of the magnetic flux density 231 of the rotor magnet 23 as a structure which contains triplex harmonics in the induced voltage of the brushless motor 10 of this invention. However, the present invention is not limited to this. For example, the harmonics may be contained in the induced voltage by arranging the teeth of the stator core in the circumferential direction.

Moreover, although the approximate sine wave sensorless drive circuit 4 was comprised on the circuit board 35 of the brushless motor 10 of this invention, this invention is not limited to this embodiment. For example, the approximate sine wave sensorless drive circuit 4 may be formed on a circuit board different from the circuit board 35 of the brushless motor 10. Moreover, the approximate sine wave sensorless drive circuit 4 may be comprised with the circuit board 35 and other circuit boards.

Moreover, although the chucking device 24 of the brushless motor 10 of this invention was equipped with the coil spring 242 and the chuck claw 243, this invention is not limited to this. For example, the chucking device may be a center case having only a careful claw to watch out for the disk, even without the coil spring 242 and the chuck claw 243. In addition to the coil spring 242, the coil spring 242 may be an elastic member that applies a force to the outside of the chuck claw 243 in the radial direction. In addition, the chuck claw 243 is not limited to embodiment. What is necessary is just a shape which can hold | maintain a disk.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section cut in the axial direction which shows one Embodiment of the brushless motor of this invention.

FIG. 2 is a schematic plan view of the brushless motor of FIG. 1 seen from above. FIG.

3 is a circuit diagram showing an approximate sine wave sensorless driving circuit of the brushless motor of the present invention.

4 is a graph showing the magnetic flux density of the rotor magnet of the brushless motor of the present invention.

5 is a magnetic flux density of the rotor magnet of the first comparative example.

Fig. 6 is a schematic plan view seen from above showing a stator mounted on a brushless motor of the present invention.

FIG. 7 is an enlarged view of a part of the stator core of the stator of FIG. 6.

8 is a graph showing the coil inductance of the stator of the present embodiment and the coil inductance of the stator of the brushless motor of the second comparative example.

It is a schematic cross section cut in the axial direction which shows one Embodiment of the disk drive apparatus of this invention.

Claims (9)

A brushless motor driven by a sensorless drive circuit, A rotating body rotating with the central axis as the rotating shaft, A rotor magnet disposed coaxially with the rotating body, A stator facing the rotor magnet, Coil wound on the stator Provided with The sensorless driving circuit drives and controls the brushless motor based on a signal including a harmonic component tripled with respect to the fundamental wave of the induced voltage, As the rotor magnet rotates with respect to the stator, the amplitude ratio of triplex harmonics to the fundamental wave of the induced voltage generated in the coil is set to be 1% or more, The ratio of the amount of change which is the difference between the maximum value and the minimum value of the coil inductance to the maximum value of the coil inductance is 10% or more. Brushless motor. As a brushless motor, A rotor having a rotor magnet coaxially with the central axis and rotating around the central axis; A stationary body having a stator facing the rotor magnet and a sensorless drive circuit for controlling rotation of the rotor by controlling energization of a coil of the stator. Respectively, The sensorless drive circuit, A position detector for detecting a rotational position of the rotor from the induced voltage generated in the coil by rotating the rotor magnet relative to the stator; A control unit for controlling the energization timing according to the positional information of the rotating body obtained by the position detecting unit; A motor driving unit for switching energization to the coil based on a control signal from the control unit, The position detection unit detects the position of the rotating body using a signal including a harmonic component tripled with respect to the fundamental wave of the induced voltage, The induced voltage is set such that the amplitude ratio of the triplex harmonics to the fundamental wave is 1% or more, The ratio of the amount of change which is the difference between the maximum value and the minimum value of the coil inductance to the maximum value of the coil inductance is 10% or more. Brushless motor. The method according to claim 1 or 2, The magnetic flux density on the side of the rotor magnet is distributed in a waveform having an approximate sinusoidal shape with respect to the rotation angle, and in the waveform, a recess is present at the center of the magnetic pole. Brushless motor. delete The method according to claim 1 or 2, The stator extends along a radial direction about a central axis, and includes a plurality of teeth portions spaced apart in a circumferential direction, The tooth portion is provided with a widening portion facing the rotor magnet and a base portion extending radially inward from the widening portion, The widening portion has an opposite surface having a width in the circumferential direction that is larger than the width in the circumferential direction of the base portion, and an inner surface provided on the opposite side of the opposite surface and the radial direction and continuous with the side surface of the base portion, A value of D1 / R1, which is a ratio of the position nearest to the rotor magnet on the opposite surface and the distance R1 connecting the central axis and the distance D1 connecting the inner surface and the central axis, is between 0 seconds and 0.92 or less. Brushless motor. The method of claim 5, The magnitude | size of the width of the said circumferential direction of the said base part is changing along the said radial direction, A value of Wmin / Wmax, which is a ratio of the maximum value Wmax of the width in the circumferential direction of the base portion and the minimum value Wmin of the width in the circumferential direction of the base portion, is 0.7 or more and less than 1 Brushless motor. The method of claim 2, The sensorless driving circuit is configured on a circuit board constituting the fixture. Brushless motor. The method according to claim 1 or 2, The rotating body includes a mounting portion for mounting a disk-shaped disk having an opening hole in the center thereof, and a chucking device for attaching and detaching the disk. Brushless motor. A disk drive device for mounting a brushless motor according to claim 8 to drive a disk, An optical pickup mechanism for emitting and receiving light from the disk; And a moving mechanism that enables the optical pickup mechanism to move in the radial direction. Disk drive.

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